ABSTRACT
The congenital heart disease series of the Pathological Museum at La Sapienza University of Rome was revised in order to detect specimens featuring atrioventricular valve dysplasia (AVVD) in fetuses and infants. Selected for study were 67 specimens from a collection of 667 hearts: there were 36 cases of isolated tricuspid valve dysplasia (TVD), 11 cases of isolated mitral valve dysplasia (MVD), and 20 cases of combined atrioventricular valve dysplasia. All the valves were graded according to Becker's criteria, which were morphometrically validated. There is an increasing degree of dysplasia in terms of differentiation and detachment of the valve from the ventricular wall. The concept of AVVD is supported by a substantial morphologic and morphometric analogy between TVD and MVD, in spite of some peculiarities of each grade and of side-specific anomalies ("mitral arcade" on the left side and grade III dysplasia on the right one), probably attributable to differences in the embryonic development of the two valves. AVVD is sometimes associated with dysplasia of the semilunar valves, in the setting of a polyvalvular disease of possible genetic origin. More often it is combined with other defects that cause ventricular overload. In such cases, AVVD usually occurs within the overloaded cardiac section, as if it were a result of mechanical stress.
ABSTRACT
Subaortic stenosis has been described with increasing frequency as an ominous feature of atrioventricular septal defect (AVSD), especially following surgical correction of the anomaly in non-Down's syndrome patients. In order to study the surgical anatomy of the left ventricular outflow tract in this malformation, 48 hearts featuring AVSD were examined. Obstructive lesions were classified into unequivocal forms (class A, 13.5%) and potential ones (class B, 10.8%). In the remaining hearts (class C, 75.7%) no obstruction was noted. In class A, subaortic stenosis was due to exaggeration of the anticipated anomalous arrangement of atrioventricular valve tensor apparatus, to the persistence of a subaortic muscular infundibulum, and to a discrete fibrous diaphragm. A potential for subaortic stenosis is provided by the unwedged position of the aortic valve. The left ventricular outflow tract is transformed into a long, forward-displaced fibromuscular channel. Morphometric analysis showed in AVSD (with both common annulus and separate orifices) a significantly (p less than 0.01) lower inflow/outflow tract ratio, and a significantly (p less than 0.01) lower right ventricular/left ventricular outflow length ratio than normal hearts. These results suggest that AVSD is characterized not only, as commonly stated, by inflow tract shortening, but by outflow tract lengthening as well. On these anatomical grounds, nearly all cases of AVSD could harbor the potential for subaortic stenosis; however, this becomes a real hazard (class B) only when associated with forward displacement of the left anterior papillary muscle, or direct insertion on the ventricular septum of the anterior bridging leaflet, and it may be converted to an actual obstruction by the effects of surgery.(ABSTRACT TRUNCATED AT 250 WORDS)